EVALUATION OF THE ECOLOGICAL AND GEOCHEMICAL PATTERNS OF NITROGEN AND PHOSPHORUS DISTRIBUTION IN THE DNIPRO RIVER`S SURFACE WATERS

The Problem Statement and Purpose. The problem of surface water pollution with nitrogen and phosphorus compounds is relevant for many world regions, including Ukraine. The main sources of these substances entering water bodies are municipal wastewater, agriculture (fertilizer use), and industry. Excessive input of nitrogen and phosphorus compounds leads to eutrophication manifesting in the mass reproduction of algae, depletion of water oxygen, and the death of aquatic organisms. To solve this problem, comprehensive measures are needed, including improving monitoring and pollution prognosis approaches. Data & Methods. An ecological and geochemical assessment was performed to analyze nitrogen and phosphorus compounds’ spatiotemporal dynamics in the surface waters of the Dnipro River. The study area encompassed seven water intakes of major Ukrainian cities, extending from Vyshhorod to Dnipro city, with data collected between 2015 and 2023. The research involved the application of mathematical statistics, encompassing the calculation of basic statistical indicators and the implementation of Pearson correlation analysis. Results. Based on the ecological and geochemical assessment of nitrogen and phosphorus distribution patterns in the Dnipro River’s surface waters, several conclusions were drawn. Periodic exceedances of maximum permissible concentrations (MPCs) of ammonium and nitrites were observed throughout the study area. More often ammonium concentrations exceeded MPCs in the water intakes of Horishni Plavni, Kyiv, and Cherkasy, while nitrites most frequently exceeded MPCs in the water intakes of Dnipro, Kyiv, and Kremenchuk. Seasonal analysis revealed elevated ammonium, phosphates, and nitrite levels during summer and early autumn. August was characterized by a concurrent increase in these substances, indicative of peak eutrophication in the Dnipro River Basin. Nitrates exhibited a distinct seasonal pattern, with the lowest concentrations occurring during summer and increasing levels during the colder months. Phosphates displayed the most pronounced seasonal fluctuations. A long-term analysis of nitrogen and phosphorus compounds indicated that ammonium concentrations reached a high in 2023 at most monitoring stations for the 2015–2023 period. Dnipro city’s water intakes showed a consistent upward trend in all nitrogen compounds. Cherkasy had the highest annual average concentrations of nitrates and phosphates. A comprehensive spatiotemporal analysis identified three distinct groups of monitoring stations based on common patterns of nitrogen and phosphorus distribution. The first includes the territories of the water intakes of Kyiv and Cherkasy, the second – Kremenchuk and Horishni Plavni, and the third – Kamyanske and Dnipro city. These groups are mostly located in different reservoirs or sub-basins. Applying ecological and geochemical assessment, including spatiotemporal analysis of various hydrochemical parameters, can provide valuable data for zoning surface waters based on the specific types of pollution and the intensity of various anthropogenic factors.